Thermodynamic Refugia in the Arabian peninsula: the diurnal moisture pulse as a physical Indicator of desert habitability

Hyper-arid deserts are traditionally viewed as thermodynamically uniform landscapes where extreme heat and chronic moisture deficits constrain biological persistence. However, this assumption overlooks localized land–atmosphere interactions that may create discrete islands of stability. Using high-resolution ERA5-Land reanalysis (2019–2024) across the Arabian Peninsula, we identify a Thermodynamic Decoupling Horizon at a mean Diurnal Temperature Range (DTR) of 12.0 °C, separating coastal advection from a radiation-dominated continental interior. Within this interior, we identify 109 spatially isolated thermodynamic refugia characterized by mean DTR values of 5.8 °C—substantially lower than the 14.0 °C observed in the surrounding Thermodynamic Void. These sites are maintained by a persistent nocturnal moisture pulse (∼44.1 g m −2 ) that enables morning evaporative buffering. Domain-wide scaling analysis ( n = 5499) indicates that this buffering operates as a non-linear, threshold-dominated process (Spearman's ρ = −0.68, p < 0.001), revealing an abrupt “hockey-stick” activation of thermal stability once critical moisture–coupling thresholds are exceeded. This mechanism truncates the high-temperature tail of the thermal distribution, reducing exposure to lethal heat stress (>35 °C) from 28.3% of total hours in the background desert to only 0.6% within refugia. Our findings demonstrate that habitability in extreme environments is governed primarily by the non-linear suppression of thermal extremes, rather than by moderation of mean temperatures. This framework provides a physics-informed basis for identifying climatically buffered habitats and guiding conservation strategies in the world's most extreme environments under accelerating climate change. • A Thermodynamic Decoupling Horizon at 12.0 °C DTR separates coastal and interior regimes. • 109 thermodynamic refugia are identified within the hyper-arid Arabian interior. • Refugia reduce exposure to lethal temperatures (>35 °C) from 28.3% to 0.6%. • Non-rainfall water inputs generate a latent heat buffer of −68.6 °C per unit moisture. • Evaporative buffering capacity is proposed as a physical indicator of desert habitability.